Plantar foot pressure distribution in patients with Hallux valgus treated by distal soft tissue...

Foot and Ankle Surgery 1998 4:35-41

Plantar foot pressure distribution in patients with Hallux valgus treated by distal soft tissue procedure and proximal metatarsal osteotomy

M. NYSKA, A. LIBERSON*, C. M c C A B E t , K. LINGEq- A N D L. K L E N E R M A N t Department of Orthopaedic Surgery, Hadassah Medical Centre, Hebrew University, Jerusalem; * Department of Orthopaedic Surgery, Bnai-Zion Medical Centre, Haifa, Israel; and t University Department of Orthopaedic and Accident Surgery, Royal Liverpool University Hospital, Liverpool, UK

Summl~l/~j The combination of a distal soft tissue procedure and proximal crescentic osteotomy of the first metatarsal corrects the main pathological deformities in Hallux valgus. Common complications of operations for Hallux valgus are transfer metatarsalgia and limitation of great toe function. Seventeen patients (29 feet) who had correction of Hallux valgus with a distal soft tissue procedure and proximal osteotomy were evaluated prospectively. The EMED system was used for an objective functional evaluation of plantar foot pressures. Clinical results: the average preoperative pain score was 2.5 points (maximal pain score 3 points). It was reduced to 1.17 points postoperatively. The score regarding difficulties in wearing shoes decreased from 2.68 (maximal score 3 points) to 1.65 points whilst for the cosmetic satisfaction decreased from 2.93 to 1.44 points. Nine feet in five patients were graded fair before the operation and the rest scored 'bad'. Following the surgery 27 feet were graded good and two feet had a fair result. Plantar foot pressures: at the hallux the area of ground contact, the ground reaction force and the force time integral all were lower in patients with Hallux valgus compared to normal subjects. Pressure-time and force-time integrals were increased on the mid-forefoot. These changes are typical of the pattern seen in patients with Hallux valgus. After operation the hallux had a longer contact time and exerted more force on the ground than before the operation. There was an increase in both pressure-time and force-time integral in the mid-forefoot region, indicative of increased loading. It is concluded that a distal soft tissue procedure and proximal osteotomy yields good clinical results and does not interfere in the function of the great toe; however, it leads to increased loading of the mid-forefoot. While performing the osteotomy this forefoot loading might be decreased by minimal plantar flexing the first metatarsal.

Keywords- foot; plantar pressures; Hallux valgus

Correspondence to: M. Nyska, MD, Department of Orthopaedic Surgery, Hadassah University Hospital, POB 12000, Ein~Kerem, Jerusalem 91120, Israel.

© 1998 Blackwell Science Ltd 35

36 M. NYSKA E T A L .

Introduction

Hallux valgus affects the structure of the foot leading to biomechanical changes. Anatomically the main features of Hallux valgus deformity includes a medial prominence, contracted soft tissue structures on the lateral side of the great toe, and increased angle between the first and second metatarsals which is linked to the severity of first metatarsal pronation [1, 2]. These anatomical changes lead to alteration in the biomechanics of the foot [3-5].

The usual pre- and postoperative assessment of the patients includes subjective variables and radiographs. The decision on the specific type of operation is based partly on clinical examination and partly on radiographic measurements [4]. Common complications of operative procedures are the development of transfer metatarsalgia which is associated with pain and limitation of great toe function [1, 6].

The development of dynamic foot pressure measurement systems has now made it possible to assess these patients objectively [7, 8]. Studies on plantar foot pressure in patients with Hallux valgus have been performed on patients undergoing resection hemiarthroplasties, distal osteotomies of the first metatarsal bone, silastic arthroplasties and fusions of the first metatarsophalangeal joint [1, 3-5, 9-12].

Mann et al. [13] advocate a combination of division of adductor hallucis reefing of the medial capsule after resection of the medial prominence and proximal crescentic osteotomy of the first metatarsal. The long-term results are reported to have corrected the deformity and relieved the symptoms.

Pedobarographic evaluation of patients with Hallux valgus deformity undergoing basal osteotomy (Chevron) and distal soft tissue release demonstrated that plantar foot pressure returned to a more normal pattern during the propulsive phase of walking with weight bearing moving towards the centre of the foot [14].

The objective evaluation of plantar foot pressure in patients with Hallux valgus undergoing soft tissue repair and proximal osteotomy as advocated by Mann is presented in this study.

Material and methods

Seventeen patients undergoing operation for the correction of the deformity were studied. Twelve

patients were operated on bilaterally and five unilaterally, a total of 29 feet. The indication for surgery was a painful bunion and/or significant difficulties in walking in shoes.

The operation included release of the distal soft tissue, excision of the medial eminence, plication of the medial part of the capsule and proximal osteotomy of the first metatarsal, as proposed by Mann et al. [13]. The distal soft tissue release was performed through separate incision in the web space between the first and second metatarsals. The adductor tendon and the intermetatarsal ligament was detached from its position in the fibular sesamoid and the base of proximal phalange [15]. The lateral capsule was cut longitudinally from the head of the first metatarsal and dissected dorsally and plantarly till the hallux could be brought easily into varus position.

During the 3 years of the study 20 patients were operated using this procedure. Three patients were not diagnosed as having plantar foot pressure and were therefore excluded from the study.

The evaluation included pre- and postoperative subjective assessment, clinical examination, radiological measurements and plantar foot pressure measurements. All the operations were performed by one of the senior authors (LK) and the subjective assessment and clinical examination were performed by one independent examiner (MN).

The subjective evaluation included assessment of pain over the bunion, difficulties experienced in wearing shoes and patient satisfaction with the cosmetic appearance. Every variable scored 3 points for maximal severity, i.e. no pain received 1 point, significant pain 2 points and severe pain 3 points. The ability to walk with regular shoes scored 1 point and if a patient could not walk even with modified shoes they scored 3 points. Normal cosmetic appearance received 1 point, normal appearance with some reservation received 2 points and poor cosmetic appearance scored 3 points. In the summary of the scoring system good results received 3 points, fair results 4-6 points and bad results 7-9 points.

The clinical examination included the appearance of the foot, whether planus, normal or cavus; toe index (1: the first toe was the longest; 2: the first toe was equal to the second; and 3: the second toe was the longest); lesser toe deformations; callosities;

© 1998 Blackwell Science Ltd, Foot and Ankle Surgery, 4, 35-41

PL ANT AR FOOT PRESSURE DISTRIBUTION 37

windlass mechanism; and joint laxity. Pain or complaints about reduction of range of motion in the first metatarsophalangeal joint, first ray mobility or metatarsalgia were noted. The pre- and postoperative weight bearing radiographs were measured for Hallux valgus angle, intermetatarsal angle (between the first and second metatarsal), and the length of the first metatarsal.

Foot pressure measurements were performed using the EMED-SF system, a commercially available electronic system for recording and evaluating the distribution of pressures on the plantar aspect of the foot. This method of measurement is based on a patent from Nicol and Hennig and operates with capacitance sensors organized in a pressure platform [16]. The signals produced are displayed as a conform picture on a monitor and a hard copy print out is available from an ink jet colour printer.

The pressure platform measures 400 x 240 mm and is set flush to a walkway 5 m long. It comprises of 2736 sensors each of which are 0.25 cm 2, with a pressure range of 0-127 Newtons /cm 2. The maximal total force which can be applied is 10 000 Newtons. Patients were required to walk barefoot at their normal pace across this platform. The data from three typical steps measured pre- and postoperatively was collected and analysed using the EMED software. A control group of ten normal, healthy, age-matched women were also asked to walk at their normal pace three times across the platform, and the data was compared.

Analysis of the steps consisted of marking seven regions of interest: heel, midfoot, lateral inter- mediate and medial forefoot, toes 2-5 and the hallux. Variables used in the analysis were the area, maximal forces and peak pressures, length of contact phases, the pressure-time and force-time integral, instant of peak pressure and force for each of the regions of interest.

Statistical analysis

The data collected were transferred from the EMED system as an ASCII format file to an SPSS/PC+ program where it was then statistically analysed. The data from the clinical evaluation and the physical measurements were typed manually into the SPSS program.

The mean and SDs of the data were calculated using a one-tailed Student t-test. Statistical significance was determined at the 95% level.

Results

The average age of the patients (two men and 15 women) was 47.8 years (range 22-68 years). The average weight was 62.5 kg and the average height was 163.5 cm. The average follow-up period was 18.2 months (range 9-34 months). Five patients had flat feet and the rest were normal; one patient had hyperlaxity of joints.

Clinical results

The average preoperative pain score was 2.5 points and 1.17 points after operation. The score for difficulties in wearing shoes decreased from 2.68 to 1.65 points, whilst that for the cosmetic satisfaction decreased from 2.93 to 1.44 points. Only two patients were graded as 'fair' before the operation, the reminder scoring badly. Following the surgery 27 feet were graded 'good' and two feet were described as having a fair result (Table 1). The patients returned to their work in 10 weeks. In two patients the first toe was shortened to be equal in length to that of the second toe and in eight feet the windlass mechanism became negative after the operation. After the operation there was no pain or complaints about the limitation of the range of motion in either the metatarsophalangeal joint or the first ray. Four patients underwent PIP fusion of the lesser toes because of clawing. Three patients (three feet) suffered from transfer metatarsalgia after the operation. They were treated conservatively.

Radiological measurements

The intermetatarsal angle between the first and second metatarsals and the first metatarsophlangeal angle were reduced significantly after the operation (Figures 1, 2; Table 2). The length of the first metatarsal was shorter by less than I mm (this was not statistically significant). After the operation there were only three feet with non-congruent first metatarsophalangeal joints compared to 13 joints before the operation.


38 M. NYSKA ET AL.

Table 1 Clinical results

Pain Shoes Cosmesis

Summary Good (3 points) Fair (4-6 points) Bad (7-9 points)

* Statistical significance = P<0.05.

Scoring

Preoperative Postoperative

2.5 + 0.49 1.17 + 0.37* 2.68 ± 0.59 1.65 ± 0.47* 2.93 ± 0.24 1.44 _+ 0.49*

0 feet 27 feet 9 feet 2 feet

20 feet 0 feet

Figure 1 Typical anteroposterior radiograph of patient with bilateral Hallux valgus deformity. The measured intermetatarsal angle of the preoperative anteroposterior radiograph on the left foot was 16 ° and the first metatarsophalangeal angle was 40 °. Note the marked subluxation of the first metatarsophalangeal joint.

Figure 2 The same patient shown in Figure i after proximal first metatarsal osteotomy and distal soft tissue release.-The measured intermetatarsal angle of the postoperative anteroposterior radiograph of the left foot was 2 ° and the first metatarsophalangeal angle was 10 °. Note the postoperative congruent first metatarsophalangeal joint.

Plantar foot pressure

Comparison of normal subjects to Hallux valgus patients is shown in Table 3. The main difference noted was the increasing load in the mid-forefoot in terms of contact area with the ground, maximal forces, maximal pressures, force-time integral and pressure-time integral. The maximal pressures were higher by 50%. At the hallux there was smaller contact area, lower maximal forces by more than 50% and lower force-time integral.

Comparisons of pre- and postoperative plantar foot pressures are shown in Table 4. After the operation the main changes included increase of

loads on the mid-forefoot in the range of 20-30% in terms of maximal forces, maximal pressures, duration of contact time, pressure-time integral and force-time integral (Figures 3, 4). At the hallux there was an increase in the contact area maximal forces and maximal pressures though, in the maximal forces, it did not reach statistical significance.

Discussion

Patients with Hallux valgus undergo typical biomechanical changes: i.e. impaired great toe function and increased load in the central metatarsals leading


P L A N T A R F O O T P R E S S U R E D I S T R I B U T I O N 39

Table 2

Radiological results Preoperative Postoperative

Intermetatarsal angle (degrees) 12.88 i 4.3 7.8 ± 4.8t First M.T. ~ joint angle (degrees) 29.6 + 10.1 17.3 ± 7.4t Length first M.T. (mm) 57.3+4.4 56.9--6.6 Congruity 13 joints 3 joints

M.T. = metatarsophalangeal; t statistical significance = P<0.05.

Table 3

Comparisons of different parameters of plantar foot pressure in normal female subjects and patients with Hallux valgus deformity

Parameters Total Heel Midfoot Lat. Mid-forefoot Med. Lat. toes Hallux forefoot forefoot (2-5)

Contact area - - - + - Maximum force - - - + - - Maximum pressure + - - + Contact time + + + + Pressure-time integral + - + Force-time integral - - + -

+, significant increase P<0.05; - , significant decrease P<0.05.

Table 4

Comparisons of different parameters of plantar foot pressure in patients with Hallux valgus deformity before and after operation s

Parameters Total Heel Midfoot Lat. Mid-forefoot Med. Lat. toes Hallux forefoot forefoot (2-5)

Contact area + - + - + Maximum force + + + ( + ) Maximum pressure + + + + Contact time + + Pressure-time integral ~ + + F0rce-time integral + + +

Distal soft tissue release and proximal base osteotomy. +, significant increase P<0.05; - , significant decrease P<0.05.

to m e t a t a r s a l g i a [6, 11, 17]. T h o u g h n o p a t i e n t

compla ined of m e t a t a r s a l g i a b e f o r e t he o p e r a t i o n ,

our p l a n t a r foo t p r e s s u r e r e su l t s s u p p o r t these

alterations.

Hughes et al. [9] a l so f o u n d a t yp i ca l p a t t e r n in the

Hallux v a l g u s foo t w i t h i n c r e a s e d p e a k p r e s s u r e s

under the m e d i a l m e t a t a r s a l h e a d s a n d a s e p a r a t e

medial p e a k u n d e r the m e t a t a r s a l r e g i o n in a l l feet

compared to the n o r m a l g r o u p w h i c h s h o w e d a

medial p e a k in o n l y 34% of cases. In o u r g r o u p the re

were n ine p a t i e n t s (52%) w i t h a s e p a r a t e m e d i a l p e a k ;

the rest of the p a t i e n t s p l a c e d p r e s s u r e on the foo t

in the mid - fo re foo t .

G o o d c l in ica l r e su l t s a re a c h i e v e d b y the c o m -

b i n a t i o n of soft t i s sue r e p a i r a n d r e a l i g n m e n t of the

f irst m e t a t a r s a l a n d a r e d u c t i o n of the i n t e r m e t a t a r s a l

angle . T h o u g h o u r f o l l o w - u p of 18 m o n t h s is r a t h e r

shor t , t he g o o d c l in ica l r e su l t s a re s im i l a r to t hose

of o the r s a n d n o c h a n g e is e x p e c t e d in e i the r the

r a d i o l o g i c a l r esu l t s or in the p l a n t a r foo t p r e s s u r e

m e a s u r e m e n t s in a l o n g e r f o l l o w - u p [15, 18-20].

R a d i o l o g i c a l l y t he re w a s 40% i m p r o v e m e n t in the

i n t e r m e t a t a r s a l a n g l e a n d 42% i m p r o v e m e n t in the

m e t a t a r s o p h a l a n g e a l jo in t angle . We c o u l d s h o w o n l y

m i n i m a l n o n - s i g n i f i c a n t s h o r t e n i n g of the f irst

me ta t a r s a l .


40 M. NYSKA ET AL.

Figure 3 Preoperative maximal plantar foot pressure in the left foot of a patient with Hallux valgus. The figure shows the typical medial and central forefoot high pressure.

Figure 4 Maximal plantar foot pressure in the left foot of patient after proximal first metatarsal osteotomy and distal soft tissue release. Note the increased pressure and contact area in the central forefoot.

In studies using different systems of measuring plantar foot pressure it has been shown that most of the operations, such as silastic implants, and distal osteotomies (e.g. Wilson, Mitchel and Keller's resection arthroplasty), interfered in the function of the great toe and caused a shift of the load laterally towards the central forefoot [4, 5, 8, 9, 11, 12, 14, 15]. The authors can demonstrate an improvement in the function of the great toe as measured by plantar foot pressure.

Pitfalls in performing proximal osteotomy may include shortening and/or elevation of the first metatarsal leading to transfer metatarsalgia. Clinically only 10% of the patients had mild transfer metatarsalgia after the operation which did not require further surgery. There was no shortening of the first metatarsal in our patients, indicating that the transfer of loads to the central forefoot may be due to the minimal elevation of the head of the first metatarsal. Therefore, while performing the osteotomy this forefoot loading might be decreased by minimal plantar flexing of the first metatarsal.

Based on the plantar foot pressure data this study shows that patients with Hallux valgus deformity have a typical pattern of medial and central forefoot 1oading. Following a distal soft tissue procedure combined with proximal osteotomy there was an improvement in the function of the great toe and an increase in central forefoot loading.

References

1 Cedell CA, Astrom M. Proximal metatarsal osteotomy in Hallux valgus. Acta Orthop Scnad 1982; 53: 1013-1018.

2 Edgar MA, Klenerman L. Hallux valgus and hallux rigidus. In: Klenerman L Ed., The Foot and Its Disorders. London: Blackwell, 1991: 57-92.

3 Eustace S, O'Byrne J, Stack J et aL Radiographic features that enable assessment of first metatarsal rotation: the role of pronation in Hallux valgus. Skeletal RadioI 1993; 22: 153-156.

4 Hutton WC, Dhanendran M. The mechanics of normal and Hallux valgus feet: a quantitative study. Clin Orthop Related Res 1981; 157: 7-13.

5 Mitskevitch V. The pressure distribution in the Hallux valgus feet before and after surgery. PMR 1992; 1 (Suppl.): 4-10.

6 Hughes J, Clark P, Klenerman L. The importance of the toes in walking. J Bone Joint Surg 1990; 27B: 245-251.


PLANTAR FOOT PRESSURE DISTRIBUTION 41

7 Alexander JI, Chao EYS, Johnson KA. The assessment of foot to ground contact forces and plantar pressure distribution: a review of the evolution of current techniques and clinical applications. Foot Ankle 1990; 11: 152-167.

8 Grace D, Hughes J, Klenerman L. A comparison of Wilson and Hohmann osteotomies in the treatment of Hallux valgus. J Bone Joint Surg 1988; 70B: 236-241.

9 Hughes J, Klenerman L. The dynamic pedobarograph. Seminars In Orthopaedics 1989; 4: 99-110.

10 Merkel KD, Katoh Y, Johnson EW et al. Mitchel osteotomy for Hallux valgus: long-term follow-up and gait analysis. Foot Ankle 1983; 3: 189-196.

11 Stokes IAF, Hutton WC, Mech MI et al. Forces under the Hallux valgus foot before and after surgery. Clin Orthop Related Res 1979; 142: 64-73.

12 Welsch F, Morlock JJ, Kerschbaumer F. Evaluation of functional results after Hallux valgus surgery with Regnaulds or Brandes procedure using dynamic pedography. PMR 1992; 1 (Suppl.): 37.

13 Mann RA. The great toe. Orthop Clinic North Am 1989; 2{): 519-533.

14 Borton DC, Stephens MM. Basal metatarsal osteotomy for Hallux valgus. J Bone Joint Surg 1994; 76B: 214-219.

15 Jensen NC, Soballe K, Christiansen SE. Correction of Hallux valgus and metatarsus primus varus using the Cedell technique. Orthopedics 1989; 12: 421-424.

16 Nicol KO, Henning EM. A Capacitance-type measuring system for exterior biomechanics. J Hum Mov Stud 1981; Y: 63-86.

17 Raymakers R, Waugh W. The treatment of metatarsalgia with Hallux valgus. J Bone Joint Surg 1971; 53B: 684-687.

18 Beverly MC, Horan FT, Hutton WC. Load cell analysis following silastic arthroplasty of the hallux, h~t Orthop 1985; 9: 101-104.

19 Mann RA, Rucidell S, Graver S. Repair of Hallux valgus with a distal soft tissue procedure and proximal metatarsal osteotomy. J Bone Joint Surg 1992; 74A: 124-129.

20 Resch S, Stenstrom A, Egund N. Proximal closing wedge osteotomy and adductor tenotomy for treatment of Hallux valgus. Foot Ankle 1989; 9: 272-280.


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